The present invention relates generally to an improved swimming pool water treatment system, and more particularly to such a system which is designed to remove undesired quantities of iron from a supply of incoming water. In the swimming pool environment, dissolved iron creates a problem due to its tendency to precipitate from the solution and form a deposit on the walls forming the liner of the pool, such as a normally plastered, painted and/or vinyl-lined pools. For aesthetic purposes, the deposits are removed from time to time at considerable expense, while at the same time causing deterioration of the lining, particularly the sealing grout between adjoining tile pieces for example.
Swimming pools are widely used throughout the world as the hub of activity including sporting activity as well as aerobic and other exercises. Athletic and other aquatic events are held in swimming pool environments, since pools permit an extension of an otherwise shortened swimming activity. Pools are commonly used in homes as well as in municipal installations including municipal parks, gardens, and the like.
Underground water forms all or part of the source of water used for pool purposes. In many regions of the United States, ground water frequently contains modest to large quantities of dissolved iron. While the presence of iron does not pose an immediate health threat, it does detract from the aesthetic appearance of a swimming pool. The iron, in ionic or iron complex form, precipitates onto the walls of the pool, thereby forming an undesirable and unsightly reddish-brown stain. This stain is necessarily removed from time to time by acid treatment coupled with high pressure or other treatment operations. In any event, cleaning operations tend to cause deterioration of the surface of the pool liner, whether the liner is fabricated from the traditional ceramic tile, or fabricated of a plastic resinous material. In ceramic tile installations, the grout which is interposed or introduced as a seal between adjacent tile pieces is frequently damaged and/or eliminated under contact from the acid cleaners and/or high pressure water sources.
Undesirable quantities of ionic and/or complex ferric or ferrous iron may be removed through chemical treatment, including such treatment techniques involving precipitation/filtration as well as ion exchange. One commonly utilized technique is that of ion exchange wherein one or more resin columns are placed in series and/or parallel with an incoming source of feed water, with the output from the exchange column being delivered directly to the pool. The disadvantage of this system is the added time required through pressure drop occasioned by the water passing through the exchange columns as well as column replacement. Another technique is to interpose an iron precipitating system directly within the line, with certain quantities of the precipitate being removed through conventional filtration, with a hypochlorite, particularly sodium hypochlorite normally being utilized as the precipitate-initiator. There are two disadvantages to this system, one being the necessity of contacting the incoming water with sufficient hypochlorite so as to cause rapid precipitation of iron oxide, the other being the added time required due to pressure drop and resulting decrease in flow rate. Needless to say, both of these systems suffer from the disadvantage of requiring rather constant attention with skilled personnel, with the ion exchange columns requiring frequent interchange and replenishment.
In accordance with the system of the present invention, a storage/reaction vessel is employed for retaining relatively large volumes of water, for example, a volume capacity which is typically about 100 times the per-minute volumetric input of the water source to the treatment system. For most residential applications, the volumetric input is approximately 7 gallons per minute. In order to preserve this volumetric flow, the typical residential system for the present invention utilizes a storage vessel having the predetermined capacity set forth above or about 500 gallons. The throughput to the storage vessel remains constant, that is, equivalent to that of the incoming stream with the output being directed directly to the pool. A branch injection circuit is operatively coupled to the storage vessel through upstream circuit removal and downstream circuit return ports. A pump is interposed in the line for continuously maintaining a flow through the branch injection circuit where both hypochlorite injection and iron precipitate removal steps are accomplished. In order to provide sufficient contact time for the iron precipitation reaction to occur, the volume of the storage vessel is at least about 50 times, and preferably about 100 times the per-minute volume input of raw iron containing water to the system. This ratio provides average contact time of 50 minutes to 100 minutes in the vessel, which is generally sufficient for effective removal of the ferric ion component present in the incoming water. Ozone may be utilized in the system as an added treatment step.
The hypochlorite is metered into the system through a metered injection site, with a controlled quantity being added during flow through the branch injection circuit. In order to maintain a hypochlorite concentration of sufficient magnitude, the flow rate through the branch injection circuit exceeds that of the input/output by a magnitude of at least about 8:1. With this ratio, a sufficient quantity of hypochlorite is injected into the water flow so that effective removal can be achieved in the storage vessel during the allotted contact time. The filtration mechanism typically employs sand filters which are effective in removing the gelatinous iron oxide precipitate, with the precipitate being, of course, totally harmless to the environment.
Therefore, it is a primary object of the present invention to provide an improved swimming pool water treatment system for removal of iron from a supply of incoming water containing undesirable quantities of dissolved iron.
It is a further object of the present invention to provide an improved swimming pool water treatment system employing a storage vessel with a branch injection circuit operatively coupled to the vessel for injection of hypochlorite into the water, and with the vessel having a volume permitting extended contact time to allow precipitation of the insoluble iron precipitate.
Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification, appended claims, and accompanying drawing.